This Application claims priority from British Patent Application No. 0019596.6 filed on Aug. 9, 2000.
The present invention relates to refrigeration cabinets, and in particular to a thermal break for use in such refrigeration cabinets, and to an improved method of assembling refrigeration cabinets including such a thermal break.
Many refrigeration cabinets, which term includes refrigerators and freezers, especially for industrial and commercial use, cooled display cabinets, morgue cabinets and the like are usually formed of metal, more typically stainless steel, for hygienic purposes, especially ease of cleaning. Typically, such cabinets include an inner stainless steel liner and an outer stainless steel carcass or shell, with the void between the liner and shell being filled with an insulating foam material to provide the desired thermal insulation. As the inside surface of the refrigeration cabinet is at a desired low temperature, and the outside surface will be at an ambient temperature, which in the case of a commercial kitchen will typically be relatively high, for example up to 40xc2x0 C., there will be thermal tracking between the inside and outside metallic surfaces of the cabinet. This reduces the efficiency of the refrigeration cabinet, since additional cooling will be required to overcome the losses due to thermal tracking. Further, the thermal tracking may lead to the formation of condensation around the door seal. This, in turn, may result in a pool of condensate on the floor. This is undesirable.
A further problem is that the majority of commercial door seals are magnetic. In particular, the door includes a rubber or plastic gasket within that is provided a magnetic strip. This is attracted to the metallic frame of the refrigeration cabinet to keep the door closed. In general, the inner and outer surfaces of the refrigeration cabinets are formed from stainless steel that has a high corrosion resistance, and is therefore a good material for forming the shell and exterior of the cabinet, as this is easy to clean and has a long life. However, such grades of stainless steel may not be magnetic. Therefore, a section of stainless steel having a higher iron content that is magnetic is used to form a door surround that will attract the magnetic strip in the door seal. However, this different grade strip is more susceptible to corrosion.
In an attempt to overcome the problems associated with thermal tracking, it is known to form a thermal break between the inside stainless steel lining of the cabinet and the outer shell using a rubber or plastic strip or break that is positioned between the liner and outer shell. However, this has not proved entirely successful as part of the outer shell, on the outside of the thermal break, will be within the cold interior of the refrigerator cabinet, and therefore thermal tracking and the associated problems will still occur. It has also been proposed to form a thermal break using a hollow plastic member. However, with such an arrangement, it is difficult to form a seal with the door gasket, and the strip has a poor appearance.
Due in part to this thermal tracking, the metallic strip that attracts the magnetic strip in the door gasket will become very cold, and, especially in freezers and other very low temperature cabinets, there is the risk that the strip will become sufficiently cold that the gasket will freeze onto the strip, therefore preventing the door from being opened without damaging the gasket. To overcome this problem, it is known to provide a heater wire behind the region of the door frame on which the door gasket seals. This heater must be positioned before the void between the inner liner and the outer shell of the cabinet is filled with foam. In some cases, especially when the void is filled with foam, damage to the heater wire occurs. In this case, the door frame cannot be heated. In an attempt to overcome this problem, it is known to mount two heaters, side-by-side, behind the door frame. In this way, in the event that one of the heaters fails, either during manufacture or in use, the other heater may be used. Clearly, the requirement to provide two heaters is undesirable due to the additional manufacturing cost. Even where two heaters are provided, in some cases, especially during the use of the refrigeration cabinet, both heaters may fail. In this case, it is not possible to replace the heaters due to the insulation between the inner liner and the outer shell of the cabinet which prevents access, and therefore it is necessary to add an additional frame on the front of the cabinet that includes a new heater element. This is undesirable as it does not have an attractive appearance.
A problem with refrigeration cabinets including a known thermal break as described above is their assembly. In particular, it is difficult to correctly position the liner within the shell, and in general requires the liner to be pulled into the cabinet from the rear while the cabinet is horizontal. This may mean that a person assembling the cabinet has to crawl under the upturned cabinet, and then pull on the liner to get this into the required position. This is likely to cause injury to the assembler, and this in turn can be very expensive to the manufacturer.
A further issue in the manufacture of refrigeration cabinets is the sub-division of the cabinet. In some cases, a cabinet will require a single door for the entire opening of the cabinet. In other cases, the cabinet will require sub-division, using cross-members, to allow multiple doors or drawers giving access to different internal parts of the cabinet. The problems of thermal tracking and the need for and provision of heating elements that apply to the outer frame of the cabinet apply also to each of these partitioning members. Further, it is necessary to determine, when the cabinet is initially being made, which partitions will be required since the cross-members and heaters must be formed and foam filled with the remainder of the cabinet.
According to a first aspect of the present invention, a refrigerator cabinet including an inner liner defining an interior of the cabinet and an outer shell is provided with a hollow member having low thermal conductivity connected between the inner liner and the outer shell around an opening of the cabinet, the hollow member including a strip of magnetic material against which a closure of the cabinet abuts, and a removable cover permitting access to the interior of the hollow member.
With the cabinet according to the present invention, an effective thermal break is provided between the inner liner and the outer shell of the cabinet. In particular, the hollow member between the inner liner and outer shell has low thermal conductivity, and therefore there is little thermal conduction or tracking across the member. Further, as the member includes the surface against which the closure of the cabinet, which may be a door or the front face of a drawer for example, no part of the outer shell is inboard of the thermal break on the cooled interior of the cabinet. Therefore, there is no bridging of the thermal break, as is the case in the prior art.
A further advantage of the arrangement of the present invention is that a heater element may be provided within the thermal break itself, namely within the hollow member. Preferably, the heater element may be provided behind the strip of magnetic material so this can directly heat the surface against which the closure abuts, and thereby prevent the freezing of the closure on the surface. The ability to provide a heater element within the hollow member of the thermal break, in particular by removal of the cover to gain access to the hollow interior of the thermal break and to add or remove a heater element at this time has considerable advantages. In particular, it becomes possible to manufacture all basic cabinets without a heater element. Then, after assembly of the basic unit, a decision can be made as to whether a heater element will be required, and only if such an element is required will one be installed. This means that the same basic unit can be formed and stocked, and when a customer requires a unit with a heater, a heater can be installed. If a customer requires a unit without a heater, the same basic unit can be used. This means that it is not necessary to stock different units that differ only in the provision of a heating element. This in turn results in a quicker turnover. A further advantage is that there is less risk of damage to a heater when this is installed than is the case where a heater is installed within the metal shell of a cabinet before being foam filled. Therefore, there is less failure of the heater element during manufacture. This in turn means that there is no requirement to provide redundant heaters in case one heater fails during manufacture. This gives a further cost advantage. Further, there is no requirement to provide spare or redundant heaters in case one fails during use, since, according to the present invention, if a heater fails in use it will be possible to access this and repair or replace this. This also leads to a cost saving. Furthermore, in the event that the heater does fail, there is no need to provide a new frame to include a new heater, as is the case in the prior art. This represents a further cost saving, and means that the attractive appearance of the cabinet can be maintained, without requiring a further, unsightly, frame being added.
It is preferred that the low thermal conductivity hollow member is formed of a plastic material. The hollow member is preferably moulded or extruded. If necessary, the member may be cut to the required size. The strip of magnetic material, which advantageously includes a stainless steel material, and which may be brushed to give an attractive appearance, is preferably bonded to the hollow plastic material. The bonding of the strip is advantageously carried out during molding or extrusion of the member. Bonding the strip to the hollow member helps ensure that the strip does not separate or peel away from the hollow member over time.
The hollow member may include a flange that abuts against the liner or shell. In this case, it is preferred that an adhesive strip is provided to attach the flange to the liner or shell. This form of attachment is advantageous both as it provides a simple yet reliable connection, but also as it provides a good seal between the member and the liner or shell. This is important as, when the void between the shell and the liner is foam filled to give the desired insulation, it is necessary to provide a seal between the liner and hollow member and between the shell and hollow member to prevent the leakage of the foam. Therefore, the use of an adhesive strip acts both as a connection and to provide the required seal.
Alternatively, or additionally, the hollow member may be provided with a clip or cleat that allows the liner and/or shell to be attached to the hollow member by an interference fit. This also provides a good, simple connection between the liner or shell and the hollow member, which also gives a good seal to prevent leakage.
As the surfaces of the liner and shell to which the hollow member is attached will generally be perpendicular to each other, it is preferred that the hollow member includes one clip or cleat for an interference fit with one of the liner and shell and includes an adhesive strip for connection to the other of the liner and shell. In this way, the hollow member may merely be pressed into the corner between the liner and the shell to connect to both.
It is preferred that the hollow member is formed as a frame for the opening of the cabinet before being installed in the cabinet as a single piece. This has the advantage that the hollow member can be more easily and neatly formed that would be the case if separate pieces were mounted individually around the opening of the cabinet. This will be especially apparent at the corners of the opening.
To form a frame, it is preferred that the ends of the hollow member at the corners are suitably mitred to give a structurally strong and clean join between the parts of the frame extending in different directions. For further rigidity, it is provided that a corner piece is provided to connect parts of the hollow member at the corners of the frame. The corner piece preferably comprises a connector having two legs spaced by an angle corresponding generally to the angle between the two parts of the hollow member. Generally, the desired angle between the two parts of the frame at the corners will be 90xc2x0, and therefore the angle between the two legs of the connector will also be about 90xc2x0. To ensure the required rigidity, it is preferred that the corner piece is formed as a unitary piece.
It is advantageous for the corner piece is formed form the same material as the hollow member. This allows for easier and more reliable connection between the corner piece and the hollow member. In particular, it is preferred that the cornet piece is formed of a plastic material, and in this case this may be ultrasonically welded to the hollow member. Advantageously, the corner piece and hollow member are formed with corresponding projections and recesses to ensure their accurate relative positioning. This may also assist the connection between the components.
It is preferred that the ends of the cover strips covering the hollow member around the opening of the cabinet are shaped or mitred to abut closely to each other at the corners of the opening. Preferably, the rear part of the strip that includes the means for connection to the hollow member is spaced back from the end of the cover strip. Preferably, the connection part is also angled away from the end of the cover strip. In this way, greater clearance around the corners may be provided. This is of particular benefit for the passage of a heater through the hollow member.
Advantageously, cross-members for sub-division of the opening of the refrigeration cabinet may be removably attached to the hollow member. In this way, it is possible to form and stock cabinets having a single opening. When a customer requires a cabinet sub-divided in a particular way, it is then possible to add the required cross-members to partition the cabinet. This is of considerable advantage over the prior art that provides no way for sub-dividing a cabinet after the initial carcass has been formed and the void between the liner and outer shell foam filled. In particular, it is possible to greatly reduce the time between the receipt of an order and delivery, since it is possible to stock basic units and then to merely add the required partitions in response to a customer order, rather than making a complete unit from scratch in accordance with the customer requirement. Further, there is no need to stock a large number of pre-formed cabinets partitioned in different ways to try and have, in stock, any configuration required by a customer. Therefore, this aspect of the present invention allows a wider range of configurations to be supplied more quickly, and with less stock than has previously been the case.
It is preferred that the partitions are formed by two hollow members are used for the thermal break of the refrigeration unit, each of which are attached to a liner that extends into the interior of the cabinet to sub-divide the interior of the cabinet, and a face panel provided between the two hollow members. With this arrangement, the hollow members act as an effective thermal break to prevent thermal tracking between the partitions in the cabinet.
The closures for the cabinet, which may include one or more doors and/or one or more drawers, preferably include a gasket on the back face of the door or face of the drawer, the gasket including a strip of magnetic material and being arranged to abut against the magnetic strip of the hollow member when the closure is closed. In this way, the closure is kept in a closed condition by the magnetic attraction between the strips in the gasket and on the hollow member.
According to a second aspect of the present invention, a method of assembling a refrigeration unit comprises the steps of forming a frame defining an opening of the cabinet from a hollow member having low thermal conductivity, providing an inner liner for defining the interior of the cabinet and providing an outer shell defining the carcass of the cabinet, joining the inner liner to the hollow member and joining the hollow member to the outer shell, and filling the void between the inner liner and the outer shell with a material having low thermal conductivity.